Ok, it looks like my lights were too bright.
To compare, first picture is white skin (M4 Angelo) under same lights as the very first picture, second picture is M4 Derek under normal lights.
Also, there are no shadows except of ambient shadows

wondering if the Basicwear has empty channels to inject morphs?
or the cheo wear?

Derek isn't that drastically different in bodyshape, I'm pretty sure you can use regular morphs in clothes to cover him.
Without it, if you create a custom morph to match his body, the process will automatically create an new channel for itself.